Conveyor for continuous proofing and baking apparatus

ABSTRACT

Conveyor chains of the type utilized in commercial ovens and proofers are provided with improved bearing support for the rotating and pivoting components of the chains. The rotating components comprising anti-friction bearings constructed from superior components which support substantial improvements in the service life of the conveyor chains. The pivoting components are provided with plain bearings and/or anti-friction coating which also function to extend the service life of the conveyor chains.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation-in-part of Application Ser. No.10/309,530 filed Dec. 4, 2002, now U.S. Pat. No. 6,666,327 currentlypending, which is a continuation of Application Ser. No. 10/000,240filed Oct. 18, 2001, now U.S. Pat. No. 6,615,977 currently pending,which is a continuation of Application Ser. No. 09/837,917 filed Apr.19, 2001, now U.S. Pat. No. 6,321,895, which is a continuation ofApplication Ser. No. 09/405,294, filed Sep. 23, 1999, now U.S. Pat. No.6,257,397.

TECHNICAL FIELD

The present invention generally relates to proofing and baking apparatusof the type utilized in large commercial bakeries, and more particularlyto an improved conveyor for use in continuous proofing and bakingapparatus which is characterized by extended service life and greateradaptability to the requirements of diverse baking operations.

BACKGROUND OF THE INVENTION

Modern large-scale commercial bakeries of the type utilized in theproduction of bread, sandwich buns, and similar dough products arefrequently equipped with continuous proofing and baking apparatus. Inthe operation of a continuous proofer and/or oven, dough to be baked isreceived in bakery pans. The bakery pans are transported on grids whichare supported on the links of a continuous chain. A drive mechanismactuates the chain to transport the bakery pans and the dough containedtherein through a proofer wherein the dough is allowed to rise and/orthrough an oven wherein the dough is baked.

FIGS. 1, 2, and 3 illustrate a link 20 of the type comprising a priorart conveyor chain utilized in continuous proofing and baking apparatus.Each link 20 of the conveyor chain includes a first connection member22, a second connection member 24, and a pair of spaced, parallel plates26. The first connection member 22 of a particular link 20 is connectedto the second connection member 24 of the next preceding link in thechain by a pin 28 (FIG. 3) which facilitates pivotal movement betweenadjacent links in the nominally vertical plane. The plates 26 areconnected to the first connection member 22 and to the second connectionmember 24 by pins 30 which facilitate relative pivotal movement betweenadjacent links in the nominally horizontal plane.

The first connection member 22 of each link 20 is provided with a pairof wheels 32. The wheels 32 support the link 20 for movement along aconveyor track 36 (FIG. 3). A wheel 34 is positioned between the plates26. The wheel 34 functions to center the link 20 in the conveyor track36.

Conveyor chains of the type illustrated in FIGS. 1-3 have gainedwidespread acceptance in the commercial baking industry and otherindustries. Notwithstanding this fact, such conveyor chains incorporatevarious deficiencies. For example, the wheels 32 which support each link20 for moving along the conveyor track comprise anti-friction bearingswhich require periodic lubrication. Lubricating the chain is timeconsuming and expensive, and is frequently overlooked by bakeryoperators. Lack of lubrication leads to bearing failure which, at aminimum, requires the conveyor to be taken out of service to facilitatereplacement of the failed bearings. As will be appreciated by thoseskilled in the art, substantially more serious consequences can and doresult from bearing failure which can require the replacement ofmultiple links of the conveyor chain, entire sections of the conveyortrack, etc.

Various factors lead to improper conveyor chain maintenance andlubrication. One of the most important involves the demands made oncommercial bakeries by their customers for continuous high levelproduction leaving no time for maintenance and lubrication procedures.An equally important factor is the lack of technicians having thetraining and experience necessary to properly perform conveyor chainmaintenance and lubrication procedures. When untrained and inexperiencedpersonnel are employed to maintain and lubricate the conveyor chainsused in continuous proofers and ovens, improper and inadequatemaintenance and lubrication result.

A related problem attendant to the use of conveyor chains comprisinglinks of the type shown in FIGS. 1-3 relates to the cleaning thereof.The lubricants which are used in the anti-friction bearings of thewheels 32 of the links 20 are incompatible with the use of water anddetergents to clean the conveyor chain. It is therefore necessary toemploy other, more costly, techniques in order to attain the level ofcleanliness required in food manufacturing operations.

Even when proper lubrication and cleaning procedures are in place, theproblems inherent in the use of the prior art chain are not resolved.Lubricant from the chain combines with debris from the dough productsbeing baked to form a sludge which cannot be disposed of except pursuantto strict EPA guidelines. When the chain is used in an oven the hightemperature environment causes the lubricant to thicken to the pointthat the bearings seize causing increased load on the conveyor drivesystem and increased chain and track wear.

SUMMARY OF THE INVENTION

The present invention comprises improvements in the design of conveyorchains adapted for use in conveyorized proofers, conveyorized ovens, andsimilar applications which overcome the foregoing and other difficultieslong since associated with the prior art. In accordance with one featureof the invention, conveyor chains intended for use in baking operationsare provided with bearings which do not require lubrication. Forexample, when used in proofers, the bearings of the conveyor chain maycomprise sleeve bearings formed from plastic materials which areself-lubricating and adapted for utilization in high temperatureenvironments of the type encountered in a bakery oven. Conveyor chainsused in ovens may be equipped with self-lubricating graphite bearings ofthe type sold by Graphite Metallizing Corporation of Yonkers, N.Y.,under the trademark GRAPHALLOY®. Alternatively, the conveyor chain maybe provided with sealed self-lubricating anti-friction bearings suitablefor high temperature applications.

The use of bearings which do not require lubrication in conveyor chainsintended for bakery applications is advantageous for at least tworeasons. First, by eliminating the lubrication function which heretoforehas proven to be problematical, substantial cost savings are effected.Of equal importance is the elimination of conveyor chain failuresstemming from improper lubrication. The elimination of the lubricationrequirement also facilitates the cleaning of the conveyor track bysimply attaching a scraper to the conveyor chain. The scraper pushesbakery debris along the track to an opening in the bottom wall thereofwhere the debris is accumulated for disposal as ordinary refuse.

The present invention comprises improvements in the bearing support forthe rotating and pivoting components of conveyor chains of the typeutilized in commercial proofers and ovens. The rotating componentscomprise anti-friction bearings constructed from superior componentswhich afford substantial improvements in the service life of theconveyor chain. The pivoting components are provided with plain bearingsand/or anti-friction coatings which also function to extend the servicelife of the conveyor chain.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the invention may be had by referenceof the following Detailed Description when taken in conjunction with theaccompanying Drawings, wherein:

FIG. 1 is an exploded perspective view of a link of a prior art conveyorchain;

FIG. 2 is a perspective view of the link of FIG. 1;

FIG. 3 is a top view of a conveyor chain comprising links of the typeshown in FIGS. 1 and 2;

FIG. 4 is a side view of a conveyor chain comprising a first embodimentof the present invention in which certain parts have been broken awaymore clearly to illustrate certain features of the invention;

FIG. 5 is a view similar to FIG. 4 showing the conveyor chain of FIG. 4operating in a vertically curved section of conveyor track;

FIG. 6 is a top view of the conveyor chain of FIG. 4 showing theconveyor chain operating in a horizontally curved section of conveyortrack;

FIG. 7 is a transverse sectional view of the conveyor chain of FIG. 4;

FIG. 8 is an enlargement of a portion of FIG. 4;

FIG. 9 is an enlargement of a portion of FIG. 6;

FIG. 10 is a view similar to FIG. 4 showing a conveyor chain having ashorter pitch as compared with that of the conveyor chain of FIG. 4;

FIG. 11 is a side view similar to FIG. 4 showing a conveyor chain havinga longer pitch as compared with that of the conveyor chain of FIG. 4;

FIG. 12 is a side view similar to FIG. 4 illustrating a conveyor chaincomprising a second embodiment of the invention;

FIG. 13 is a side view similar to FIG. 4 illustrating a conveyor chaincomprising a third embodiment of the invention;

FIG. 14 is a side view of a conveyor chain comprising a fourth andpreferred embodiment of the invention in which certain parts have beenbroken away more clearly to illustrate certain features of theinvention;

FIG. 15 is a side view of the conveyor chain of FIG. 14 showing theconveyor chain operating in a vertically curved section conveyor track;

FIG. 16 is a top view of the conveyor chain of FIG. 14 showing theconveyor chain operating in a horizontally curved section of conveyortrack;

FIG. 17 is a transverse sectional view of the conveyor chain of FIG. 14;

FIG. 18 is an enlargement of a portion of FIG. 14;

FIG. 19 is a view similar to FIG. 14 illustrating a conveyor chainhaving a longer pitch as compared with that of the conveyor chain ofFIG. 14;

FIG. 20 is a diagrammatic illustration of a conveyor chain drivemechanism useful in the practice of the invention;

FIG. 21 is a diagrammatic illustration of a conveyor chain drivemechanism comprising a variation of the conveyor chain drive mechanismof FIG. 20;

FIG. 22 is a diagrammatic illustration of the conveyor chain drivemechanism of FIG. 21 showing the utilization thereof in conjunction witha conveyor chain having a longer pitch as compared with that of theconveyor chain of FIG. 18;

FIG. 23 is an illustration similar to FIG. 18 showing a variation of thepreferred embodiment of the invention;

FIG. 24 is a diagrammatic illustration of a conveyor chain drivemechanism useful in conjunction with the apparatus of FIG. 23;

FIG. 25 is a perspective view of a portion of a conveyor chainincorporating the present invention;

FIG. 26 is an exploded view of the conveyor chain of FIG. 25;

FIG. 27 is an enlarged view illustrating a component of the conveyorchain of FIG. 25;

FIG. 28 is a side view of a subassembly of the conveyor chain of FIG.25;

FIG. 29 is a sectional view taken along the line 29—29 in FIG. 28 in thedirection of the arrows; and

FIG. 30 is a sectional view taken along the line 30—30 in FIG. 28 in thedirection of the arrows.

DETAILED DESCRIPTION

Referring now to the Drawings, and particularly to FIGS. 4, 5, 6, 7, 8,and 9 thereof, there is shown a conveyor chain 50 comprising a firstembodiment of the invention. The conveyor chain 50 comprises a pluralityof identical compact carriages 52 which are connected end to end by aplurality of identical connection members 54. The conveyor chain 50operates in a conveyor track 56 comprising a solid bottom wall 58;opposed, solid side walls 60; and a top wall 62 having a center slot 64formed therein.

Each of the compact carriages 52 comprises a unitary structure which maybe manufactured from a variety of materials utilizing conventionalmanufacturing techniques. For example, the compact carriages 52 may bemanufactured from steel and/or other metals by means of die casting,investment casting, or other well known manufacturing processes.Alternatively, the compact carriages 52 may be formed from variousplastic materials suitable for high temperature applications, and may bemanufactured utilizing conventional processes such as injection molding.Preferably, the material and the process used in the manufacture ofcompact carriages 52 are selected such that few if any machiningoperations are required in order to complete the manufacture thereof.

Each compact carriage 52 comprises an elongate body 74 having identicalopenings 76 formed in the opposite ends thereof. Each opening 76receives a spherical bushing 78 which in turn receives the end portionof one of the connection members 54. The spherical bushings 78 areretained in the openings 76 by pins 80.

Axles 82 extend through the body 74 at points situated inwardly from theopening 76. The axles 82 support pairs of wheels 84 which in turnsupport the conveyor chain 54 for movement along the track 56. Bosses 86extend upwardly from the body 74 and in turn support a grid (not shown)which receives and transports bakery pans having dough received thereinalong the length of the track 56. The bosses 86 may be provided withdrilled and tapped apertures 88 which receive threaded fasteners tosecure the grid thereto. Examples of grids which may be used in thepractice of the invention are shown and described in U.S. Pat. Nos.4,729,470, 4,760,911, and 4,836,360, all of which are owned by theassignee hereof and incorporated herein by reference.

Each of the bosses 86 may have a dimensionally reduced portion 90 at theupper end thereof. Top plates 92 are supported on the bosses 86 andreceive the portions 90 therethrough. The top plates 92 function toprevent debris from entering the track 56 through the slot 64.

Each compact carriage 52 is further provided with a pair of wheels 100.The wheels 100 function to locate the compact carriage 52 relative tothe side walls 60 of the track 56. The wheels 100 are rotatablysupported on a pin 102 extending through the body 74 of the compactcarriage 52. As is best shown in FIG. 7, the wheels 100 cooperate withthe wheels 84 to completely prevent bending and tipping of the conveyorchain 50.

Referring particularly to FIG. 9, the wheels 84 are secured to the axle82 for rotation therewith. The axles 82 of conveyors intended for use inproofers may be supported by a self-lubricating plastic bearing 104which may be of the type manufactured by Igus Spritzgussteile fur dieIndustrie GmbH (Igus) of Koln (Cologne), Germany and sold under thetrademark IGLIDE®. In oven applications the self-lubricating bearings104 may be of the type sold by Graphite Metallizing Corporation ofYonkers, N.Y., under the trademark GRAPHALLOY®. The bearings 104 do notrequire lubrication in order to rotatably support the axles 82 and thewheels 84 supported thereon. Therefore, by means of the presentinvention, the need for lubrication of the wheels which support thecarriages 52 is eliminated as are the problems attended to the failureto provide required lubrication and difficulties associated withcleaning conveyor chains in which lubricating fluids are used. As isshown in FIG. 4, the wheels 84 may be rotatably supported by sealedself-lubricating anti-friction bearings 105 in lieu of the plasticbearings 104.

In accordance with one embodiment of the invention, the antifrictionbearings 105 are constructed as follows:

ABEC-9 precision 4-point contact deep groove antifriction bearings,either ball bearings or cylindrical roller bearings, comprising:

-   -   -   Highly polished races (≦1.0 μin. rms);        -   Races constructed from silicon nitride ceramic or cobalt            alloy (Stellite®)        -   Silicon nitride balls or rollers with sphericity <2 μin.,            surface finish <0.15 μin. Ra, and diameter variation <3            μin.;        -   Radial internal clearance between about 39.37 μin. and about            0.0018 in.;        -   Races and balls or rollers coated with a solid lubricant            using an ion deposition technique;        -   The solid lubricant having a thickness of between about            2,000 and about 20,000 angstroms and comprising a material            selected from the group consisting of:        -   tungsten disulfide, molybdenum disulfide, titanium nitride,            silver, carbide diamond, and boron nitride;        -   Self-lubricating retainer formed from a material selected            from the group consisting of: Vespel® (polyamide),            molybdenum disulfide impregnated Teflon®, graphite, and            fiberglass reinforced phenolic;        -   Internal volume of the bearing completely filled with a high            temperature solid lubricant selected from the group            consisting of molybdenum disulfide, graphite, and grease            impregnated polytetrafluroethylene polymer (PTFE).        -   Bearing seal selected from the group consisting of:            labyrinth fiberglass reinforced PTFE seals; viton rubber            seals with stainless steel backings; and stainless steel            shields with a 0.001″ gap between the inner race;        -   Heat stabilized to continuous exposure at 800° F.

In accordance with another embodiment of the invention, the antifrictionbearings 105 are constructed as follows:

-   -   Ball bearings or cylindrical roller bearings comprising:        -   Precision or semi-precision races (≦45.0 μin. rms);        -   Races constructed from a temperature resistant material            selected from the group consisting of T1 high temperature            tool steel, BG-42 high temperature corrosion resistant tool            steel, M2 high temperature tool steel, M50 high temperature            tool steel, High Molybdenum 440C stainless steel, 440C            stainless steel, Cronidur 30® nitrited corrosion resistant            tool steel, and 52100 bearing steel;        -   Balls or rollers selected from the group consisting of            silicon nitride, alumina, zirconia, silicon carbide, 52100            bearing steel, 440C stainless steel, BG-42 high temperature            corrosion resistant tool steel, M50 high temperature tool            steel with sphericity <20 μin., surface finish <1.6 μin. Ra,            and diameter variation <40 μin.;        -   Radial internal clearance between about 39.37 μin. and about            0.0126 in.;        -   Races and balls or rollers coated with tungsten disulfide            solid lubricant using an air impingement spray technique;        -   The solid lubricant having a thickness of between about            2,000 angstroms and about 0.003 in.;        -   Two-piece riveted stainless steel retainer with tight ball            pockets and coated with tungsten disulfide solid film            lubricant;        -   Internal volume of the bearing completely filled with a high            temperature solid lubricant comprising graphite;        -   Bearing sealed with a fiberglass reinforced PTFE seals with            stainless steel backings;        -   Heat stabilized to continuous exposure at 662° F.

In accordance with yet another embodiment of the invention, theantifriction bearings 105 are constructed as follows:

-   -   ABEC-1 precision deep groove (Conrad or gothic arch type) ball        bearings, self-aligning ball bearings, angular contact ball        bearings, cylindrical roller bearings, spherical roller        bearings, tapered roller bearings, thrust ball roller bearings,        Sheedy® roller bearings, or needle roller bearings, comprising:        -   Polished races (≦12 μin. rms);        -   Races constructed BG-42 high temperature corrosion resistant            tool steel or 440C stainless steel with an S2 heat treatment            per ASTM-A756;        -   Silicon nitride balls or rollers with sphericity <4 μin.            surface finish, <0.15 μin. Ra, and diameter variation <5            μin.;        -   Radial internal clearance between about 39.37 μin. and about            0.0126 in.;        -   Races coated with tungsten disulfide solid lubricant applied            by air impingement;        -   Two piece stainless steel (305 SS) riveted retainer with            tight ball or roller pockets;        -   Internal volume of the bearing completely filled with a high            temperature solid lubricant comprising graphite;        -   Bearing sealed with fiberglass reinforced PTFE seals with            stainless steel (302 SS) shield backings;        -   Heat stabilized to continuous exposure at 662° F.

Referring to FIG. 8, the wheels 100 are rotatably supported on the pin102. Self-lubricating antifriction bearings 106 also manufactured byIgus as described hereinabove in connection with the bearings 105 areprovided at the opposite ends of the pin 102 and in turn rotatablysupport the wheels 100 thereon. Again, the use of self-lubricatingbearings 106 to rotatably support the wheels 100 on the pin 102eliminates the need for lubrication.

As is best shown in FIGS. 6 and 9, each connection member 54 has an eye108 at each end thereof. Each eye 108 receives the spherical bushing 78of one of the compact carriages 52. In this manner, the eyes 108 of theconnection members 54 and the spherical bushings 78 of the compactcarriages 52 facilitate the movement of the conveyor chain 50 alonginclined and curved portions of the track 56. For example, FIG. 5illustrates the movement of the conveyor chain 50 along a verticallycurved portion 110 of the track 56. FIG. 6 illustrates the movement ofthe conveyor chain 50 along a horizontally curved portion 112 of thetrack 56. As will be appreciated by reference to FIGS. 5 and 6, themovement of the conveyor chain 50 along vertically and horizontallycurved portions of the track 56 is accomplished without interferencebetween the conveyor chain 50 and the track 56.

FIG. 7 illustrates the relationship between the wheels 84 and 100 of theconveyor chain 50 and the track 56. The wheels 84 travel along thebottom wall 58 of the track 56 and support the conveyor chain 50 of themovement through the track 56. The wheels 100 serve to center theconveyor chain 50 in the track 56 and to prevent interference of theconveyor chain 50 with the track 56 as the conveyor chain 50 movestherethrough. Again, the wheels 84 and 100 cooperate to prevent bendingand tipping of the conveyor chain 50.

Referring to FIGS. 10 and 11, one of the advantages in the use of theconveyor chain in the present invention comprises the adaptabilitythereof to changes in pitch. Thus, in FIG. 10 the compact carriages 52are connected end to end by connection members 54′ which aresubstantially shorter than the connection members 54 of the embodimentof the invention illustrated in FIGS. 4, 5, and 6. The use of theconnection members 54′ in lieu of the connection members 54 results in aconveyor chain 50 having a substantially shorter pitch. The use of aconveyor chain having a shorter pitch is advantageous in those instancesin which the conveyor chain is used to transport either heavier bakerypans or bakery pans carrying heavier loads as compared with the loadingof a conveyor chain having a longer pitch.

Referring to FIG. 11, there is shown a conveyor chain 50 wherein thecompact carriages 52 are connected end to end by connection members 54″which are substantially longer than the connection members 54 of theconveyor chain 50 illustrated in FIGS. 4, 5, and 6. The use of thelonger connection members 54″ in the conveyor chain 50 of FIG. 9 resultsin the conveyor chain having a substantially longer pitch as comparedwith the pitch of the conveyor chain 50 shown in FIGS. 4, 5, and 6. Theuse of a conveyor chain having a longer pitch is advantageous in thoseinstances in which the conveyor chain is called upon to carry eitherlighter bakery pans or bakery pans carrying lighter loads as comparedwith the loading of the conveyor chain 50 of FIGS. 4, 5, and 6.

Referring to FIG. 12, there is shown a conveyor chain 150 comprising asecond embodiment of the invention. The conveyor chain 150 comprises aplurality of identical compact carriages 152 which are connected end toend by a plurality of identical connection members 154. The conveyorchain 150 operates in a conveyor track 156 comprising a solid bottomwall 158; opposed, solid side walls 160; and a top wall 162 having acenter slot formed therein.

Each of the compact carriages 152 comprises a unitary structure whichmay be manufactured from a variety of materials utilizing conventionalmanufacturing techniques. For example, the compact carriages 152 may bemanufactured from steel and/or other metals by means of die casting,investment casting, or other well known manufacturing processes.Alternatively, the compact carriages 152 may be formed from variousplastic materials adapted for high temperature applications, and may bemanufactured utilizing conventional processes such as injection molding.Preferably, the materials and the process used in the manufacture ofcompact carriages 152 are selected such that few if any machiningoperations are required in order to complete the manufacture thereof.

Each compact carriage 152 comprises an elongate body 174 havingidentical openings 176 formed in the opposite ends thereof. Each opening176 receives a spherical bushing 178 which in turn receives the endportion of one of the connection members 154. The spherical bushings 178are retained in the openings 176 by pins 180.

Axles 182 extend through the body 174 at points situated inwardly fromthe opening 176. The axles 182 support pairs of wheels 184 which centerthe conveyor chain 150 in its movement along the track 156. The axlesare extended downwardly to prevent excess tipping of the compactcarriages. A boss 186 extends upwardly from the body 174 and in turnsupport a grid (not shown) which receives and transports bakery panshaving dough received therein along the length of the track 156. Theboss 186 may be provided with a drilled and tapped aperture 188 whichreceives a threaded fastener to secure the grid thereto. Examples ofgrids which may be used in the practice of the invention are shown anddescribed in U.S. Pat. Nos. 4,729,470, 4,760,911, and 4,836,360, all ofwhich are owned by the assignee hereof and incorporated herein byreference.

Each boss 186 may have a dimensionally reduced portion 190 at the upperend thereof. A top plate 192 is supported on each boss 186 and receivesthe portion 190 therethrough. The top plates function to prevent debrisfrom entering the track 156 through the slot in the top wall 162.

Each compact carriage 152 is further provided with a pair of wheels 200.The wheels 200 function to support the compact carriage 152 for movementalong the bottom wall 158 of the track 156. The wheels 200 are rotatablysupported on a pin 202 extending through the body 174 of the compactcarriage 152.

The wheels 184 are secured to the axle 182 for rotation therewith. Eachaxle 182 is rotatably supported by a self-lubricating bearing 204. Thebearings 204 do not require lubrication in order to rotatably supportthe axles 182 and the wheels 184 supported thereon. Therefore, by meansof the present invention, the need for lubrication of the wheels whichsupport the carriages 152 is eliminated as are the problems attendant tothe failure to provide required lubrication and difficulties associatedwith cleaning conveyor chains in which lubricating fluids are used.

Like the rotational support for the wheels 184, the wheels 200 aresecured to the pin 202. A self-lubricating bearing 206 rotatablysupports the pin 202 and the wheels 200 mounted thereon. Again, the useof the self-lubricating bearings 206 to rotatably support the wheels 200and the pin 202 eliminates the need for lubrication.

Each connector member 154 has an eye 208 at each end thereof. Each eye208 receives a spherical bushing 178 of one of the compact carriages152. In this manner, the eyes 208 of the connection members 154 and thespherical bushings 178 of the compact carriages 152 facilitate themovement of the conveyor chain 150 along vertically and horizontallycurved portions of the track 156.

Referring to FIG. 13, there is shown a conveyor chain 250 comprising athird embodiment of the invention. The conveyor chain 250 comprises aplurality of identical compact carriages 252 which are connected atequally spaced intervals along a wire rope 254. The conveyor chain 250operates in a conveyor track 256 comprising a solid bottom wall 258;opposed, solid side walls 260; and a top wall 262 having a center slotformed therein.

Each of the compact carriages 252 comprises a unitary structure whichmay be manufactured from a variety of materials utilizing conventionalmanufacturing techniques. For example, the compact carriages 252 may bemanufactured from steel and/or other metals by means of die casting,investment casting, or other well known manufacturing processes.Alternatively, the compact carriages 252 may be formed from variousplastic materials suitable for high temperature applications, and may bemanufactured utilizing conventional processes such as injection molding.Preferably, the material and the process used in the manufacture ofcompact carriages 252 are selected such that few if any machiningoperations are required in order to complete the manufacture thereof.

Each compact carriage 252 comprises a elongate body 274 having anopening 276 extending axially therethrough. The opening 276 receives thewire rope 254. Compression sleeves 278 mounted on the wire rope 254locate and secure each compact carriage 252 thereon.

Axles 282 extend outwardly from the body 274 at points situated inwardlyfrom ends thereof. The axles 282 support pairs of wheels 284 whichcenter conveyor chain 250 for moving along the track 256. A boss 286extends upwardly from the body 274 and in turn supports a grid (notshown) which receives and transports bakery pans having dough receivedtherein along the length of the track 276. The boss 286 may be providedwith a drilled and tapped aperture which receives a threaded fastener tosecure the grid thereto. Examples of grids which may be used in thepractice of the invention are shown and described in U.S. Pat. Nos.4,729,470, 4,760,911, and 4,836,360, all of which are owned by theassignee hereof and incorporated herein by reference.

The boss 286 may have a dimensionally reduced portion at the upper endthereof. A top plate may be supported on the boss 286 and receive thedimensionally reduced portion therethrough. If used, the top platesfunction to prevent debris from entering the track 256 through the slotin the top wall 262.

Each compact carriage 252 is further provided with a pair of wheels 300.The wheels 300 function to support the compact carriage 52 for movementalong the bottom wall of the track 256. The wheels 300 are rotatablysupported on pins 302 extending from the body 274 of the compactcarriage 252.

The wheels 284 are each rotatably supported by a self-lubricatingantifriction bearing constructed as disclosed hereinabove in connectionwith the bearing 105. The self-lubricating bearings do not requirelubrication in order to rotatably support the wheels 284. Therefore, bymeans of the present invention, the need for lubrication of the wheelswhich support the carriages 252 is eliminated as are the problemsattendent to the failure to provide required lubrication anddifficulties associated with cleaning conveyor chains in whichlubricating fluids are used. The wheels 300 are also rotatably supportedby self-lubricating bearings.

Referring to FIGS. 14, 15, 16, 17, and 18, there is shown a conveyorchain 350 comprising a fourth and preferred embodiment of the invention.The conveyor chain 350 comprises a plurality of identical links 352which are connected end to end to form the chain 350. The conveyor chain350 comprising the links 352 is adapted for movement along the length ofa conveyor track 356 comprising a solid bottom wall 358; opposed, solidside walls 360; and a top wall 362 having a central slot formed therein.

Each component of the links 352 comprises a unitary structure which maybe manufactured from a variety of materials utilizing conventionalmanufacturing techniques. For example, the links 352 may be manufacturedfrom steel and/or other metals by means of die casting, investmentcasting, or other well known manufacturing processes. Alternatively, thelinks may be formed from various plastic materials adapted for hightemperature applications, and may be manufactured utilizing conventionalprocesses such as injection molding. Preferably, the material and theprocess used in the manufacture of links are selected such that few ifany machining operations are required in order to complete themanufacture thereof.

Each link 352 comprises a first link portion 364 and a second linkportion 366. Each first link portion 364 is connected to itscorresponding second link portion 366 by a pin 368 which facilitatesrelative pivotal movement between the link portions in the nominallyvertical plane. Each pin 368 also has mounted thereon a pair of wheels370 which support the link 352 for movement along the bottom wall 358 ofthe track 356.

The second link portion 366 of each link 352 is connected to the firstlink portion 364 of the immediately following link 352 by a pin 372.Thus, the pins 372 facilitate relative pivotal movement of the links 352of the conveyor chain 350 in the nominally horizontal plane. Each pin372 also supports two wheels 374 which serve to center the conveyorchain 350 and the track 356. As is best shown in FIG. 17, the diametersof the wheels 370 and 374 are closely matched to the interior dimensionsof the track 356 whereby the wheels 370 and 374 completely preventbending or tipping of the chain 350.

The pins 368 and 372 of the links 352 facilitate the movement of theconveyor chain 350 along inclined and curved portions of the track 356.For example, FIG. 15 illustrates the movement of the conveyor chain 350along a vertically curved portion of the track 356. FIG. 16 illustratesthe movement of the conveyor chain 350 along a horizontally curvedportion of the track 356. As will be appreciated by reference to FIGS.15 and 16, the movement of the conveyor chain 350 along inclined andcurved portions of the track 356 is accomplished without interferencebetween the conveyor chain 350 and the track 356.

Referring particularly to FIGS. 14, 16, 17, and 18, the wheels 370 arerotatably supported on the pins 368 by self-lubricating bearings 376which are preferably constructed as described hereinabove in connectionwith bearings 105. Likewise, the wheels 374 are rotatably supported onthe pins 372 by self-lubricating bearings 378. The use of theself-lubricating bearings 376 and 378 to rotatably support the wheels370 and 374, respectively, eliminates the need for lubrication. As isshown in FIG. 14, the wheels 370 and 374 may be supported by sealedself-lubricating anti-friction bearings 379 adapted for high temperatureapplications in lieu of the bearings 376 and 378.

Each first portion 364 of each link 352 includes a boss 380 extendingupwardly therefrom and through the slot in the top wall 362 of the track356. Each boss 380 supports a grid (not shown) which receives andtransports bakery pans having dough received therein along the length ofthe track 356. Each boss 380 may be provided with a drilled and tappedaperture 382 which receives a threaded fastener to secure the gridthereto. Examples of grids which may be used in the practice of theinvention are shown and described in U.S. Pat. Nos. 4,729,470;4,760,911; and 4,836,360, all of which are owned the assignee hereof andincorporated herein by reference.

Each boss 380 may have a dimensionally reduced portion 384 at the upperend thereof. Top plates 386 are supported on the bosses 380 and receivethe portions 384 therethrough. The top plates function to prevent debrisfrom entering the track 356 through the slot in the top wall 362thereof.

Referring to FIG. 19, one of the advantages of the use of the conveyorchain in the present invention comprises the adaptability thereof tochanges in pitch. Thus, in FIG. 19 there is shown a conveyor chain 350having links 352′ which are substantially longer than the links 352 ofthe conveyor chain 350 illustrated in FIGS. 14, 15, and 16. The use ofthe longer links 352′ in the conveyor chain of FIG. 19 results in theconveyor chain having a substantially longer pitch as compared with thepitch of the conveyor chain 350 shown in FIGS. 14, 15, and 16. The useof a conveyor chain having a longer pitch is advantageous in thoseinstances in which the conveyor chain is called upon to carry eitherlighter bakery pans or bakery pans carrying lighter loads as comparedwith the loading of the conveyor chain 350 of FIGS. 14, 15, and 16.

Referring now to FIG. 20, there is shown a drive mechanism 400 useful inconjunction with all of the conveyor chains illustrated in FIGS. 4through 19, inclusive, and described hereinabove in conjunctiontherewith. The drive mechanism 400 includes a drive chain 402 which istrained around an idler sprocket 404, an idler sprocket 406, and a drivesprocket 407. The drive sprocket 407 is actuated by a suitable drivemechanism to cause the drive chain 402 to move around the course definedby the sprockets 404 and 406.

A plurality of chain engaging members 408 are supported on the drivechain 402 for engagement therewith. Each chain engaging member 408includes a forward roller 410 which is rotatably supported on a pin 412secured in the drive chain 402 and a rearward roller 414 which followsthe surface of a cam 416 extending adjacent to the path of the drivechain 402.

Referring particularly to the portion of the cam 416 extending adjacentto the idler sprocket 406, if the rollers 410 and 412 were both securedto the drive chain 402, the chain engaging members 408 would accelerateduring movement around the idler roller 406. However, utilizing themeans of the engagement of the roller 414 with the cam 416, each chainengaging member 408 remains parallel to its corresponding surface on theconveyor chain until the chain engaging member 408 has moved downwardlyfar enough to disengage from the conveyor chain. In this manneroperating power is applied to the conveyor chain evenly and withoutperiodic intervals of acceleration as would otherwise be the case.

FIG. 21 illustrates an alternative drive mechanism 420 which may beutilized in the practice of the invention. The drive mechanism 420includes a drive chain 422 which extends around a course defined by adrive sprocket 424 and two idler sprockets 426 and 428.

The drive mechanism further includes a plurality of conveyor chainengaging members 430 each dimensioned to fully fill the space betweenadjacent links of a conveyor chain. In this manner the drive mechanism420 may be utilized to apply a breaking force to the conveyor chain.This is accomplished by slowly reducing the operating power that issupplied to the drive sprocket 424 or by completely reversing thedirection of operation of the drive sprocket 424 depending upon therequirements of particular circumstances.

Each conveyor chain engaging member 430 is secured to the drive chain422 by a pin. Each conveyor chain engaging member 430 is provided with aforward roller 434 and a rearward roller 436. The rearward roller 436follows a cam which is substantially identical in shape and function tothe cam 416 illustrated in FIG. 20. Thus, the rearward roller 436 causesthe conveyor chain engaging member 430 to disengage from the conveyorchain without applying acceleration thereto.

The forward roller 434 of each conveyor chain engaging member 430follows a track 438. The movement of the forward roller 434 in the track438 causes each conveyor chain engaging member 430 to enter into thespace between adjacent links of the conveyor chain without applyingeither acceleration forces or deceleration forces thereto. Thus, theconveyor chain engaging member moves smoothly into the gap betweenadjacent links of the conveyor chain and into engagement with both ofthe adjacent links without applying forces thereto which otherwise wouldtend to change the speed of travel of the conveyor chain.

FIG. 22 illustrates the use of the drive mechanism 420 in thoseinstances in which the pitch of the conveyor chain is too long for theconveyor engaging members 430 to fill the entire gap between adjacentlinks of the conveyor chain. In such instances a spacer 440 is mountedon each connection member of the conveyor chain at a suitable locationbetween adjacent links thereof so as to receive the chain engagingmember 430 between the spacer 440 and the link of the conveyor chainsituated forwardly thereof. In this manner the drive mechanism 420functions identically to the manner in which it functions as illustratedin FIG. 21 but without the necessity of employing conveyor engagingmembers which are unduly long.

Referring to FIGS. 23 and 24, there is shown a conveyor chain 450comprising a variation of the conveyor chain 350 illustrated in FIGS. 14through 18, inclusive, and described hereinabove in conjunctiontherewith. The conveyor chain 450 is identical to the conveyor chain 350except that it comprises identical links 352′ each having upper andlower drive cams 452 and 454 secured thereto by fasteners 456.

FIG. 24 illustrates a drive mechanism 460 useful in conjunction with theconveyor chain 450. The drive mechanism 460 includes a drive motor 462which actuates a drive sprocket 464. A drive chain 466 is trained aroundthe drive sprocket 464 and two idler sprockets 468 and 470.

A drive chain cam 472 extends between the idler sprockets 468 and 470.The drive chain 466 carries a plurality of drive forks 476. Uponactuation by the drive motor 462, the drive sprocket 464 actuates thedrive chain 466 to move the drive forks 476 around a course extendingfrom the drive sprocket 464 around the idler sprocket 468, across thedrive chain cam 472, around the idler sprocket 470, and back to thedrive sprocket 464.

As each drive fork 476 moves into engagement with the drive chain cam472 it is gradually lifted into engagement with one of the drive cams452 on one of the links 352′ of the conveyor chain 450, being understoodthat an identical drive fork engages the drive cam 454 on the oppositeside of the particular link 352′. As will be appreciated by thoseskilled in the art, the drive chain 466 and the conveyor chain 450 moveat the same speed. Therefore, the drive forks of the conveyor chain 466engage the drive cams of the conveyor chain 450 without applying anyacceleration force or any deceleration to the conveyor chain 450.Subsequently, the drive chain cam 472 gradually lowers each drive fork476 out of engagement with the drive cam 452 with which it has beenengaged. Again, the disengagement between the drive forks and the drivecams is accomplished without applying any acceleration force ordeceleration force to the conveyor chain 450.

FIGS. 25 through 30, inclusive, illustrate a link 520 useful in theconstruction of conveyor chains of the type used in continuous proofingand baking apparatus. Each link 520 of the conveyor chain includes afirst connection member 522, a second connection member 524, and a pairof spaced, parallel plates 526. The first connection member 522 of aparticular link 20 is connected to the second connection member 524 ofthe next preceding link in the chain by a horizontal pin 523 whichfacilitates pivotal movement between adjacent links in the nominallyvertical plane. The plates 526 are connected to the first connectionmember 522 and to the second connection member 524 by vertical pins 530which facilitate relative pivotal movement between adjacent links in thenominally horizontal plane. Each connection member 524 is provided witha boss 525 which is used to support and position a product pansupporting grid (not shown).

The first connection member 522 of each link 520 is provided with a pairof wheels 532 which are rotatably supported on pins 531 by antifrictionbearings constructed as described hereinabove in connection withbearings 105. The pins 531 are provided with one or more removablefasteners 533 to facilitate replacement of the wheels 532. The wheels532 support the link 520 for movement along a conveyor track. A wheel534 is positioned between the plates 526. The wheels 534 are rotatablysupported on pins 530 by antifriction bearings constructed as describedhereinabove in connection with bearings 105 and function to center thelink 520 in the conveyor track.

The pins 523 and 530 are provided with a thin solid film lubricantselected from the group including molybdenum disulfide, tungstendisulfide, graphite, titanium nitrite, diamond carbide, and alloys ofnickel. The solid film lubricant has a thickness ≦0.001 in. Referringparticularly to FIG. 27, the connection members 522 and 524 may beprovided with self-lubricating plain bearings 536 each formed from amaterial selected from the group comprising graphite, reinforcedpolytetrafluroethylene, and bronze. Bearings 536 are press fit or heatshrunk into the bores comprising the connection members 522 and 524.Alternatively, in lieu of the bearings 536 the entirety of theconnection members 522 and 524 may be coated with a thin film solidlubricant selected from the group including molybdenum disulfide,tungsten disulfide, graphite, titanium nitrite, diamond carbide, andalloys of nickel.

Although preferred embodiments of the invention have been illustrated inthe accompanying Drawings and described in the foregoing DetailedDescription, it will be understood that the invention is not limited tothe embodiments disclosed, but is capable of numerous rearrangements,modifications, and substitutions of parts and elements without departingfrom the spirit of the invention.

1. In a conveyor for commercial proofers and ovens of the typecomprising: a conveyor track of the type having a bottom wall, opposedside walls, and a top wall having a slot formed therein; and a conveyorchain including a plurality of substantially identical carriages eachcomprising: (a) an elongate body extending between first and secondends; (b) at least one first wheel pair supported on the body forrotation about an axis located adjacent the first end of the body; (c)self-lubricated bearings supporting the first wheel pair for rotationrelative to the body; (d) a second wheel pair supported on the body at alocation between the first and second ends for rotation about an axisextending perpendicularly to the axis of rotation of the first wheelpair; (e) self-lubricated bearings supporting the second wheel pair forrotation relative to the body; and means connecting the first end of oneof each carriage to the second end of the next adjacent carriage in theconveyor chain; wherein the self-lubricated bearings supporting thefirst and second wheel pairs comprise antifriction bearings including:races having a surface finish of ≦45.0 □in. rms and constructed from atemperature resistant material selected from the group consisting ofsilicon nitride ceramic, Stellite®, T1 high temperature tool steel,BG-42 high temperature corrosion resistant tool steel, M2 hightemperature tool steel, M50 high temperature tool steel, high molybdenum440C stainless steel, 440C stainless steel, Cronidur 30® nitritedcorrosion resistant tool steel, and 52100 bearing steel; balls formedfrom a material selected from the group consisting of silicon nitride,alumina, zirconia, silicon carbide, 52100 bearing steel, 440C stainlesssteel, BG-42 high temperature corrosion resistant tool steel, M50 hightemperature tool steel and characterized by: sphericity <20 □in.,surface finish <1.6 □in. Ra, and diameter variation <40 □in.; radialinternal clearance between about 39.37 □in. and about 0.0126 in.; racesand balls coated with a solid lubricant having a thickness of betweenabout 2,000 angstroms and about 0.003 in. and comprising a materialselected from the group consisting of: tungsten disulfide, molybdenumdisulfide, titanium nitride, silver, carbide diamond, and boron nitride;self-lubricating retainers formed from a material selected from thegroup consisting of: Vespel® (polyamide), molybdenum disulfideimpregnated Teflon®, graphite, fiberglass reinforced phenolic; andstainless steel coated with tungsten disulfide solid lubricant; theinternal volumes of the bearings being completely filled with a hightemperature solid lubricant selected from the group consisting ofmolybdenum disulfide, graphite, and grease impregnatedpolytetrafluoroethylene (PTFE); and bearing seals selected from thegroup consisting of: labyrinth fiberglass reinforced PTFE seals; vitonrubber seals with stainless steel backings; and stainless steel shieldswith a 0.001″ gap between the inner race.
 2. The conveyor according toclaim 1 wherein the self-lubricating bearings comprise races having asurface finish ≦12 □in. rms.
 3. The conveyor according to claim 1wherein the self-lubricated bearings comprise races having a surfacefinish ≦1.0 □in. rms.
 4. The conveyor according to claim 1 wherein theself-lubricated bearings comprise races formed from a material selectedfrom the group consisting of BG-42 high temperature corrosion resistanttool steel and 440C stainless steel.
 5. The conveyor according to claim1 wherein the self-lubricated bearings comprise races constructed from amaterial selected from the group consisting of T1 high temperature toolsteel, BG-42 high temperature corrosion resistant tool steel, M2 hightemperature tool steel, M50 high temperature tool steel, high molybdenum440C stainless steel, 440C stainless steel, Cronidur 30 ® nitritedcorrosion resistant tool steel, and 52100 bearing steel.
 6. The conveyoraccording to claim 1 wherein the self-lubricated bearings comprise racesconstructed from a material selected from the group consisting ofsilicon nitride ceramic and Stellite®.
 7. The conveyor according toclaim 1 wherein the self-lubricated bearings comprise balls formed fromsilicon nitride and characterized by a sphericity <4 □in., a surfacefinish, <0.15 □in. Ra, and a diameter variation <5 □in.
 8. The conveyoraccording to claim 1 wherein the balls are formed from silicon nitrideand are characterized by a sphericity <20 □in., a surface finish <1.6□in. Ra, and a diameter variation <40 □in.
 9. The conveyor according toclaim 1 wherein the self-lubricated bearings comprise balls formed fromsilicon nitride characterized by a sphericity <2 □in., a surface finish<0.15 □in. Ra, and a diameter variation <3 □in.
 10. The conveyoraccording to claim 1 wherein the self-lubricated bearings arecharacterized by an internal radial clearance of between about 39.37□inc. and about 0.0018 in.
 11. The conveyor according to claim 1 whereinthe self-lubricated bearings comprise balls coated with an airimpingement applied tungsten disulfide solid lubricant.
 12. The conveyoraccording to claim 1 wherein the self-lubricated bearings comprise ballscoated with an ion deposition applied tungsten disulfide solidlubricant.
 13. The conveyor according to claim 1 wherein theself-lubricated bearings comprise an internal volume completely filledwith a high temperature solid lubricant comprising graphite.
 14. Theconveyor according to claim 1 wherein the self-lubricated bearingscomprise an internal volume completely filled with a solid lubricantformed from a material selected from the group consisting of molybdenumdisulfide and grease impregnated polytetrafluoroethylene polymer. 15.The conveyor according to claim 1 wherein the self-lubricated bearingsare further characterized by self lubricating retainers formed from amaterial selected from the group consisting of Vespel®, molybdenumdisulfide impregnated Teflon®, graphite, and fiberglass reinforcedphenolic.
 16. The conveyor according to claim 1 wherein the selflubricated bearings are further characterized by fiberglass reinforcedpolytetrafluoroethylene seals with stainless steel backings.
 17. Theconveyor according to claim 1 wherein the self-lubricated bearings arefurther characterized by bearing seals selected from the groupconsisting of labyrinth fiberglass reinforced PTFE seals; viton rubberseals with stainless steel backings; and stainless steel shields.
 18. Ina conveyor for commercial proofers and ovens of the type comprising: aconveyor track of the type having a bottom wall, opposed side walls, anda top wall having a slot formed therein; and a conveyor chain includinga plurality of substantially identical carriages each comprising: (a) anelongate body extending between first and second ends; (b) at least onefirst wheel pair supported on the body for rotation about an axislocated adjacent the first end of the body; (c) self-lubricated bearingssupporting the first wheel pair for rotation relative to the body; (d) asecond wheel pair supported on the body at a location between the firstand second ends for rotation about an axis extending perpendicularly tothe axis of rotation of the first wheel pair; (e) self-lubricatedbearings supporting the second wheel pair for rotation relative to thebody; and means connecting the first end of one of each carriage to thesecond end of the next adjacent carriage in the conveyor chain; whereinthe self-lubricated bearings supporting the first and second wheel pairscomprise antifriction bearings including: races having a surface finishof ≦45.0 □in. rms and constructed from a temperature resistant materialselected from the group consisting of silicon nitride ceramic,Stellite®, T1 high temperature tool steel, BG-42 high temperaturecorrosion resistant tool steel, M2 high temperature tool steel, M50 hightemperature tool steel, high molybdenum 440C stainless steel, 440Cstainless steel, Cronidur 30® nitrited corrosion resistant tool steel,and 52100 bearing steel; rollers formed from a material selected fromthe group consisting of silicon nitride, alumina, zirconia, siliconcarbide, 52100 bearing steel, 440C steel, BG-42 high temperaturecorrosion resistant tool steel, M50 high temperature tool steel andcharacterized by: sphericity <20 □in., surface finish <1.6 □in. Ra, anddiameter variation <40 □in.; radial internal clearance between about39.37 □in. and about 0.0126 in.; races and rollers coated with a solidlubricant having a thickness of between about 2,000 angstroms and about0.003 in. and comprising a material selected from the group consistingof: tungsten disulfide, molybdenum disulfide, titanium nitride, silver,carbide diamond, and boron nitride; self-lubricating retainers formedfrom a material selected from the group consisting of: Vespel®(polyamide), molybdenum disulfide impregnated Teflon®, graphite,fiberglass reinforced phenolic; and stainless steel coated with tungstendisulfide solid lubricant; the internal volumes of the bearings beingcompletely filled with a high temperature solid lubricant selected fromthe group consisting of molybdenum disulfide, graphite, and greaseimpregnated polytetrafluoroethylene (PTFE); and bearing seals selectedfrom the group consisting of: labyrinth fiberglass reinforced PTFEseals; viton rubber seals with stainless steel backings; and stainlesssteel shields with a 0.001″ gap between the inner race.
 19. The conveyoraccording to claim 18 wherein the self lubricating bearings compriseraces having a surface finish ≦12 □in. rms.
 20. The conveyor accordingto claim 18 wherein the self-lubricated bearings comprise races having asurface finish ≦1.0 □in. rms.
 21. The conveyor according to claim 18wherein the self-lubricated bearings comprise races formed from amaterial selected from the group consisting of BG-42 high temperaturecorrosion resistant tool steel and 440C stainless steel.
 22. Theconveyor according to claim 18 wherein the self-lubricated bearingscomprise races constructed from a material selected from the groupconsisting of T1 high temperature tool steel, BG-42 high temperaturecorrosion resistant tool steel, M2 high temperature tool steel, M50 hightemperature tool steel, high molybdenum 440C stainless steel, 440Cstainless steel, Cronidur 30® nitrited corrosion resistant tool steel,and 52100 bearing steel.
 23. The conveyor according to claim 18 whereinthe self-lubricated bearings comprise races constructed from a materialselected from the group consisting of silicon nitride ceramic andStellite®.
 24. The conveyor according to claim 18 wherein theself-lubricated bearings comprise rollers formed from silicon nitrideand characterized by a sphericity <4 □in., a surface finish, <0.15 □in.Ra, and a diameter variation <5 □in.
 25. The conveyor according to claim18 wherein the rollers are formed from silicon nitride and arecharacterized by a sphericity <20 □in., a surface finish <1.6 □in. Ra,and a diameter variation <40 □in.
 26. The conveyor according to claim 18wherein the self-lubricated bearings comprise rollers formed fromsilicon nitride characterized by a sphericity <2 □in., a surface finish<0.15 □in. Ra, a diameter variation <3 □in.
 27. The conveyor accordingto claim 18 wherein the self-lubricated bearings are characterized by aninternal radial clearance of between about 39.37 □inc. and about 0.0018in.
 28. The conveyor according to claim 18 wherein the self-lubricatedbearings comprise rollers coated with an air impingement appliedtungsten disulfide solid lubricant.
 29. The conveyor according to claim18 wherein the self-lubricated bearings comprise balls coated with anion deposition applied tungsten disulfide solid lubricant.
 30. Theconveyor according to claim 18 wherein the self-lubricated bearingscomprise an internal volume completely filled with a high temperaturesolid lubricant comprising graphite.
 31. The conveyor according to claim18 wherein the self-lubricated bearings comprise an internal volumecompletely filled with a solid lubricant formed from a material selectedfrom the group consisting of molybdenum disulfide and grease impregnatedpolytetrafluoroethylene polymer.
 32. The conveyor according to claim 18wherein the self-lubricated bearings are further characterized by selflubricating retainers formed from a material selected from the groupconsisting of Vespel®, molybdenum disulfide impregnated Teflon®,graphite, and fiberglass reinforced phenolic.
 33. The conveyor accordingto claim 18 wherein the self lubricated bearings are furthercharacterized by fiberglass reinforced polytetrafluoroethylene sealswith stainless steel backings.
 34. The conveyor according to claim 18wherein the self-lubricated bearings are further characterized bybearing seals selected from the group consisting of labyrinth fiberglassreinforced PTFE seals; viton rubber seals with stainless steel backings;and stainless steel shields.
 35. In a conveyor for commercial proofersand ovens of the type comprising: a conveyor track of the type having abottom wall, opposed side walls, and a top wall having a slot formedtherein; and a conveyor chain including a plurality of substantiallyidentical carriages each comprising: (a) an elongate body extendingbetween first and second ends; (b) at least two first wheels supportedon the body for rotation about an axis located adjacent the first end ofthe body; (c) self-lubricated bearing means supporting the first wheelsfor rotation relative to the body; (d) at least two second wheelssupported on the body at a location between the first and second endsfor rotation about an axis extending perpendicularly to the axis ofrotation of the first wheels; (e) self-lubricated bearing meanssupporting the second wheels for rotation relative to the body; andmeans connecting the first end of one of each carriage to the second endof the next adjacent carriage in the conveyor chain; the means forconnecting the first end of each carriage to the second end of the nextadjacent carriage comprising apertures formed in the first and secondends of each carriage and pins received in the apertures for pivotallyconnecting the carriages one to another; the apertures and the pinsbeing self-lubricated to facilitate relative pivotal movement betweenadjacent carriages.
 36. The conveyor according to claim 35 wherein thepins which pivotally connect the first and second ends of adjacentcarriages are coated with a solid film lubricant formed from a materialselected from the group consisting of molybdenum disulfide, tungstendisulfide, graphite, titanium nitrite, diamond carbide, and alloys ofnickel.
 37. The conveyor according to claim 36 wherein the solid filmlubricant has a thickness of <0.0001 in.
 38. The conveyor according toclaim 35 wherein the apertures which pivotally connect the first andsecond ends of adjacent carriages are coated with a solid film lubricantformed from a material selected from the group consisting of molybdenumdisulfide, tungsten disulfide, graphite, titanium nitrite, diamondcarbide, and alloys of nickel.
 39. The conveyor according to claim 38wherein the solid film lubricant has a thickness of <0.0001 in.
 40. Theconveyor according to claim 35 wherein the apertures which pivotallyconnect the first and second ends of adjacent carriages comprise plainbearings formed from a material selected from the group consisting ofgraphite, reinforced polytetrafluroethylene, and bronze.